1. Field of the Invention
The invention relates to a singulation metal mold used for producing a semiconductor device packaged in a package such as BGA (Ball Grid Array) which is thin and compact and has outer dimensions close to that of a semiconductor chip, and a method for producing the semiconductor device including a singulation step by using the singulation metal mold. Herein “singulation” means dividing or cutting a base film or tape on which plural semiconductor chips are mounted into pieces on each of which the single semiconductor chip is mounted.
2. Description of the Related Art
Heretofore, a TAB (Tape Automated Bonding) system is used to produce such type of a semiconductor device for improving the productivity.
FIG. 4 shows an example of a semiconductor device having a mounting structure in BGA or CSP (Chip Size Package) system. The semiconductor device 100 is constructed such that a wiring 102 is formed on the surface of an insulating substrate 101 with an opening 120 where a circuit board 103 is composed of the 101 and 102, and a semiconductor chip 105 is mounted on the circuit board 103 through an elastic material 104. Furthermore, the whole circumference of the semiconductor chip 105 and the opening 120 as a space housing an electrode pad 108 is sealed with a sealing resin 106 by transfer molding.
In detail, the wiring board 103 is arranged such that apertures 121 for attaching solder balls 107 for external connection are defined on the lengthy insulating substrate 101 called also a carrier tape, and the wiring 102 is formed by photo-etching a copper foil which is previously laminated on a surface for mounting the semiconductor chip 105. The solder balls 107 are attached to the back surface opposite to the surface for mounting the semiconductor chip 105.
The semiconductor chip 105 is mounted on the circuit board 103 through the elastic material 104, and the electrode pad 108 disposed on the bottom of the semiconductor chip 105 is connected to the wiring 102, whereby the electrical connection is made therebetween.
The plural semiconductor devices 100 arrayed and formed on the single continuous and lengthy carrier tape according to the TAB system as described above need to be finally separated into single chip-mounted packages. Namely, it is necessary to conduct a singulation step for singulating the semiconductor devices 100 on the carrier tape (insulating substrate 101).
FIGS. 5A to 5C are cross sectional views showing steps for singulating semiconductor devices as described above and the singulation metal mold used therefor.
In the singulating steps, at first, as shown in FIG. 5A, a TAB tape 111 with the semiconductor devices 100 sealed but not separated into the respective pieces is mounted on a singulation metal mold 110.
Then, as shown in FIG. 5B, punches 112 as a upper metal mold of the singulation metal mold 110 descend to sandwich the semiconductor devices 100, which are arrayed and formed at predetermined regions on the TAB tape, between the punches 112 and a die block 113, and, while engaging the punches 112 with the die block 113 as a lower metal mold, a predetermined pressure is applied thereon by press work. Thus, the insulating substrate 101, the elastic material 104, the sealing resin 106 and, optionally, a plating electric current supplying extension line (not shown) for the wiring 102 are punched simultaneously. As a result of the punching, the respective semiconductor devices 100 are separated one another as so-called individual piece.
Here, the respective semiconductor devices 100 are left on a knockout 114 inside the die block 113. Then, the knockout 114 located on a knockout press-up plate 115 is pressed up by elevating the knockout press-up plate 115 as shown in FIG. 5C, so that the semiconductor devices 100 left on the surface of the knockout 114 are disposed higher than the upper surface of the die block 113. In this state, a suction collet 116 is brought close to the semiconductor device 100 from above, and the semiconductor 100 is picked up by applying suction force by air pressure (negative pressure).
When the pick-up work is completed, the knockout press-up plate 115 is moved down by an actuator (not shown) such as an air cylinder disposed outside the singulation metal mold 110. Thus, since nothing supports the knockout 14, the knockout 114 freely falls with its own weight to return to a regular low position. Alternatively, as a power source for pressing up the knockout 114, spring force is proposed instead of the air cylinder (See JP-A-H01-183830).
However, irrespective of which types of the power source is used to press up the knockout 114, a very thin and fine chip of the sealing resin etc. may be produced unavoidably during the singulation, where the chip can penetrate the clearance between the knockout 114 and the die block 113 to clog it.
In the chip-clogged state, the smooth vertical movement of the knockout 114 in the die block 113 is highly disturbed. Thus, as shown in FIG. 6A, the knockouts 114b and 114c being normally movable in the vertical direction freely falls down to a normal low position, and only the knockout 114a which cannot be smoothly moved due to the clogging with the chip 117 is left at an upper position.
When the singulation is conducted under the above conditions, as shown in FIG. 6B and FIG. 7 which is an enlarged cross sectional view of FIG. 6B, while the semiconductor device 100 is clamped between the punch 112 and the knockout 114a, an excessive pressure will be applied to the semiconductor device 100. When the excessive pressure is applied thereto, the serious defect in the semiconductor device 100 as a target product is more likely to occur. Namely, cracks may be caused on the outer shell (the sealing resin 106 and the like) of a mounting package of the semiconductor device 100, or the breakage or serious damage of the semiconductor chip 105 may be caused inside the sealing resin 106.
Under the circumstances, it may be considered that such a minute dimension that the chip 117 cannot absolutely intrude into a clearance between the knockout 114 and the die block 113 is adopted in order to avoid the clogging with the chip 117. In fact, however, it is required that the clearance between the knockout 114 and the die block 113 is at least 0.5 mm, or more in order to assure the smooth vertical movements of the knockout 114. Consequently, it is extremely difficult or impossible to avoid the incidence of clogging with the thin chip 117 of 0.5 mm or less, and further it makes more difficult to overcome the problem of the incidence of serious defects in the semiconductor device 100 in the singulating step.
As mentioned above, in the conventional singulation metal mold and the conventional method for producing the semiconductor device using the singulation metal mold by the conventional TAB system, there is the problem that the breakage, damage or the like of the semiconductor device may be caused by a failure in the free fall of the knockout inside the metal mold during the singulation. It is very difficult to solve the above problem.